What Do L-Carnitine Supplements Really Do?

L-carnitineAlso known as levocarnitineit is an amino acid that occurs naturally in the body and is available as a supplement. It is a subtype of the substance carnitine, which aids metabolism and can be used to prevent carnitine deficiency.

L-carnitine produces energy in the body and removes toxins from cells. Because of this action, L-carnitine is sometimes taken as a supplement to lose weight and improve physical performance.

This article will discuss the uses of L-carnitine and its role in the body.

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L-carnitine: what it does and what it doesn’t do

L-carnitine is a crucial component of energy production in the body. Moves fatty acids into cells to be converted into energy. L-carnitine also helps remove toxins from cells.

It can help with various symptoms of different diseases and conditions, as described below.

Alzheimer’s disease

Alzheimer’s disease is a progressive, neurodegenerative (wasting of nerve cells in the brain) condition and the most common type of dementia. It can be treated by preventing breakdown or by increasing levels of the neurotransmitter called acetylcholine.

Researchers have studied L-carnitine to determine if it can help produce acetylcholine.

A 2020 review of several articles regarding the use of L-carnitine for dementia and Alzheimer’s disease found mixed results. Many of the studies reviewed showed favorable results with the use of L-carnitine, while other studies showed little or no results.

More research is needed on the effects of L-carnitine on people with Alzheimer’s disease.

Cardiovascular disease

L-carnitine supplements might aid in cardiovascular health by decreasing markers of inflammation and reducing the likelihood of fatal irregular heart rhythms in people with heart disease.

A 2017 study found benefits from L-carnitine supplementation in people with chronic heart failure. Improvements in several areas of heart function, including cardiac output and left ventricular ejection fraction.

Other studies have found that L-carnitine supplementation caused negative effects on the cardiovascular system. Research has yet to be conducted to determine whether L-carnitine supplementation is an effective treatment for cardiovascular disease.

Weight loss

L-carnitine moves fatty acids into cells for energy, so it has been speculated that L-carnitine may help with weight loss. There are some studies that support this theory, but more research is needed to draw any conclusions.

A literature review looking at 37 randomized control trials found that L-carnitine reduced body weight by 1.21 kilograms (kg) (2.66 lbs). The weight reduction was mostly seen in people who also followed a low-calorie diet and exercised.

Athletic performance

Carnitine stores fuel for muscles and aids in the breakdown of fat into energy. As a result, some people take L-carnitine supplements to enhance their athletic performance.

However, research has shown no evidence that L-carnitine supplements improve exercise performance.


L-carnitine has been used successfully to improve fertility. Research has shown that supplementation has improved sperm motility.

Other research has shown that L-carnitine supplementation has improved ovulation and pregnancy rates in those with polycystic ovary syndrome (PCOS). Those people with PCOS who took the supplement had 64.4 percent higher ovulation rates. It has also improved pregnancy rates and reduced miscarriages in those with PCOS.

Daily dosage of L-carnitine

Carnitine is produced in the liver, kidneys and brain. The body stores 95% of carnitine in the heart and skeletal muscles. The body needs 15 milligrams (mg) of carnitine per day from external sources such as food or the body making its own carnitine.

Most people eating a diet of both meat and non-meat sources will consume between 24 and 145 mg of carnitine each day. However, people following a vegan diet will likely only consume 1.2 mg per day.

Oddly enough, diet doesn’t appear to affect the amount of carnitine the body produces. According to the National Institutes of Health, a person following a vegan diet still produces 14.4 mg of carnitine per day.

Because carnitine is a supplement, the Food and Drug Administration (FDA) does not regulate it, and there are no recommended daily amounts of supplementation.

Types of L-carnitine supplements

L-carnitine is a type of carnitine. There are several forms of carnitine available for supplementation. They include:

  • L-carnitine: The most popular and least expensive form of carnitine. Its absorption rate ranges from 14% to 18%.
  • Acetyl-L-carnitine: This is absorbed more easily in the intestines and crosses the blood-brain barrier. As a result, it is more likely to be used in patients with Alzheimer’s disease.
  • Propionyl-L-carnitine: This form of carnitine is used in those with heart and peripheral vascular disease.

Carnitine is usually taken as an oral supplement, but can be given through an intravenous (IV) line.

L-carnitine side effects

There are potential side effects when taking too much L-carnitine. They include:

  • Vomit
  • Nausea
  • Diarrhea
  • Abdominal cramps
  • Muscle weakness
  • Bad body odor
  • Convulsions

Some medications, such as those that treat seizures or antibiotics, lower levels of carnitine in the body. Taking a carnitine supplement can help avoid this. Always talk to a doctor before starting a carnitine supplement.

L-carnitine in food

The best source of L-carnitine is in food. The body’s ability to absorb L-carnitine from food is much higher than from a supplement. The best sources (listed from greatest to lowest) of L-carnitine are:

  • Beef, including steaks and ground beef
  • Whole milk
  • Salted cod
  • Chicken breast
  • Ice-cream
  • Cheese


L-carnitine is an amino acid that is produced in the body and is found in many food products of animal origin. Produces energy and removes toxins from cells. L-Carnitine is often advertised as a supplement for weight loss, to enhance physical performance, and more.

Research still needs to be done to confirm the effectiveness of L-carnitine supplementation. Always talk to a healthcare professional before starting a supplement as it may interact negatively with other medications or affect certain conditions.

Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read about our editorial process to learn more about how we fact check and keep our content accurate, reliable and trustworthy.

  1. National Institute of Health. Carnitine.

  2. Centers for disease control and prevention. Alzheimer’s disease and related dementias.

  3. Pennisi M, Lanza G, Cantone M, et al. Acetyl-l-carnitine in dementia and other cognitive disorders: a critical update.Nutrients. 2020;12(5):1389. doi:10.3390/nu12051389

  4. Song X, Qu H, Yang Z, Rong J, Cai W, Zhou H. Efficacy and safety of l-carnitine treatment for chronic heart failure: a meta-analysis of randomized controlled trials.BioMed Research International. 2017;2017:1-11. doi:10.1155/2017/6274854

  5. Talenezhad N, Mohammadi M, Ramezani-Jolfaie N, Mozaffari-Khosravi H, Salehi-Abargouei A. Effects of l-carnitine supplementation on weight loss and body composition: a systematic review and meta-analysis of 37 clinical trials randomized controlled trials with dose-response analysis.Clinical Nutrition ESPEN. 2020;37:9-23. doi:10.1016/j.clnesp.2020.03.008

  6. Gnoni A, Longo S, Gnoni GV, Giudetti AM. Carnitine in human muscle bioenergetics: Can carnitine supplementation improve exercise?Molecules. 2020;25(1):182. doi:10.3390/molecules25010182

  7. Mount Sinai. Carnitine (l-carnitine).

  8. Mendelson SD. Dietary supplements and metabolic syndrome. In:Metabolic syndrome and psychiatric disease. Elsevier; 2008:141-186. doi:10.1016/B978-012374240-7.50012-7

By Patty Weasler, RN, BSN

Patty is a Registered Nurse with over a decade of experience in the Pediatric ICU. Her passion is to write health and wellness content that anyone can understand and use.

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